Fuel tanks which hold a volume of fuel, for example gasoline or diesel fuel, to be supplied to an internal combustion engine of a motor vehicle are known to include a fuel level sensor which generates a signal indicative of the fuel level within the fuel tank. The signal is provided to a fuel level gauge which delivers a visual display to an operator of the motor vehicle to keep the operator informed of the quantity of fuel remaining in the fuel tank. One known fuel level sensor includes a ceramic card with a resistive circuit disposed thereon and also includes a wiper assembly which makes sliding contact with the resistive circuit. The wiper assembly is attached to a float which changes the position of the wiper assembly on the resistive circuit. Consequently, when an electric current is applied to an input side of the wiper assembly, the signal resulting at an output side of the wiper assembly will vary depending on the position of the wiper assembly relative to the resistive circuit. One such fuel level sensor is illustrated in U.S. Pat. No. 6,681,628 to Sawert et al., the disclosure of which is incorporated herein by reference in its entirety.
The sliding interface between the resistive circuit and the wiper assembly, and the harsh environment within which the fuel level sensor is located, present challenges in durability. Consequently, precious metals are commonly used to survive the harsh environment and provide good electrical contact. In one known arrangement, the wiper assembly includes a soft gold contact surface which engages the resistive circuit which is silver-based. While this arrangement limits gold, which is relatively expensive, to the wiper assembly, soft gold may have a shorter service life than is desirable. In another known arrangement, the wiper assembly includes a hard gold contact surface which engages the resistive circuit. While the hard gold contact surface increases the durability of the wiper assembly, the service life of the silver-based resistive circuit may be shorter than is desirable due to the hard gold with which the silver-based resistive circuit interfaces. Consequently, when a hard gold contact surface is used on the wiper assembly, it is typical for the resistive circuit to be gold-based in order to provide an acceptable service life since the gold-on-gold sliding interaction is more durable than the gold-on-silver sliding interaction. While fuel level sensors which include a wiper assembly having a hard gold contact surface and a gold-based resistive circuit on the ceramic card provide a satisfactory service life, the cost of such an arrangement may be prohibitive to implement because of the increased amount of gold in the fuel level sensor.
What is needed is an electrical connection and a fuel level sensor which minimizes or eliminates one or more of the shortcomings as set forth above.